Fire-fighting foam is a stable aggregation of small bubbles having a lower density than oil or water, and typically exhibits tenacity for covering horizontal surfaces. Mixing air into a solution of water that contains foam concentrate creates air foam. Air foam tends to flow freely over a burning liquid surface and form a tough, air-excluding, continuous blanket that seals volatile combustible vapors from access to air. A foam blanket of this nature resists disruption from wind and draft, or heat and flame attack, and is capable of resealing in case of mechanical rupture. Fire-fighting foams usually retain such properties for relatively long periods of time and are useful for fighting fires in many ordinary combustible materials, such as wood, cloth, paper, rubber, and many plastics; as well as fires in many flammable liquids, oils, greases, tars, oil base paints, lacquers, and flammable gases.
The uses of foam for fire fighting and fire suppression have increased greatly since the foam was first used in the 1930s. As the technology for using the foam developed over the years, new systems for applying foam were developed, as were new foam-forming liquid concentrates. A relatively early development (circa 1954) included the application of foam from overhead sprinkler-type systems using specially designed foam-making nozzles. These nozzles were capable of forming foam from protein-type foam concentrate solutions, or delivering a satisfactory water discharge pattern when supplied only with water. By way of example, protein, fluoroprotein, aqueous film-forming concentrates, and film-forming fluoroprotein foam (AFFF) concentrates are materials suitable for use with foam-water sprinkler systems.
Foam-water sprinkler systems are typically pipe-connected to both a source of foam concentrate and a source of water. These systems are also equipped with appropriate devices for discharging and distributing a foam/water solution over a particular area. The discharge devices are connected to the water supply by way of a control valve, known as a “proportioning valve”, which is usually actuated by automatic detection equipment installed in the same areas as the discharge devices. When the proportioning valve opens, water flows through the valve and is mixed with foam concentrate that is simultaneously injected into the water stream. The resulting foam solution is then discharged from the system though the various discharge devices. Upon exhaustion of the supply of foam concentrate, water discharge typically continues until it is shut off manually. Existing deluge sprinkler systems that have been converted to aqueous film forming foam or film forming fluoroprotein foam systems are usually considered to be foam-water sprinkler systems.
In general, “proportioning” is the process of mixing or combining two or more ingredients into a common product at a predetermined ratio. For fire fighting and suppression, there are numerous known proportioning systems and methods, including: (i) the premixed foam solution method; (ii) Venturi (vacuum inducing); (iii) pressure proportioning; (iv) bladder tank proportioning; (v) balance pressure proportioning; (vi) in-line balanced pressure proportioning; (vii) around the pump proportioning; (viii) pick-up nozzles; and (ix) jet pump proportioning. It is important that a proportioning system be able to consistently maintain the correct ratio of foam concentrate to water across the entire proportioning range indicated by a particular system. If proportioning is too “lean” (i.e., less than the design-specified percentage of foam to water), the overall foam quality decreases. The drainage time decreases and the bubbles break faster, thereby resulting in less resistance to heat. Thus, lean foam may not put out the fire. Alternately, if proportioning is too rich (i.e., greater than the design-specified percentage of foam concentrate to water), the foam will exhibit stiffness and non-fluidity or reluctance to flow around obstructions. Additionally, the supply of foam concentrate will be depleted more rapidly and may not adequately meet minimum operating time requirements. Thus, the overall operability and performance of a proportioning system should be characterized; both when the system is installed and at regular intervals thereafter.
As an international standards organization, the National Fire Protection Association (NFPA) has developed standards for the testing of certain fire-related equipment, including foam-water sprinkler systems and other systems. Among these standards are Standards 11, 16, 25 and 409. Standard 25 (“NFPA 25”) is the “Standard for Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems” and requires inspection, testing, and maintenance of water-based fire protection systems. NFPA 25 provides guidelines for each inspection, testing, and maintenance activity that must be performed on a daily, weekly, monthly, quarterly, annually, or over 5, 10, and 20-year intervals. Compliance with NFPA 25 is important for reasons of: (i) owner liability, because the standard clearly places the responsibility for a working sprinkler system on the owner of the building in which the system has been installed; and (ii) cost, because performing regular maintenance helps avoid the expense associated with repairing or replacing multiple system components all at once. However, due to expense commonly associated with testing (e.g., of the foam itself and of disposing of the foam used in the test), and other difficulties associated with actually conducting an adequate system tests, many foam-water sprinkler systems are seldom, if ever, tested by building owners or other responsible parties. As a result, many of these systems may operate less than optimally or may fail when they are needed. Thus, there is a need for an effective and inexpensive system and method for testing fire fighting and fire suppression systems that utilize solutions of water and fire fighting foam.